This application concerns the completion of a longitudinal study of psychiatric epidemiology as it relates to data already collected for the period 1952 to 1970 and then extension through the gathering of new data about the period 1970 to 1990. Named the Stirling County Study, the investigation involves multiple cross- sectional surveys and several cohort follow-up studies pertinent to 2848 adult residents of a rapidly changing rural environment in Atlantic Canada. The objectives of the study are to contribute information on trends in prevalence, incidence, outcomes (mortality and morbidity), and treatment of psychiatric disorders in a general population and to relate these variables to risk factors about physical health, life events, and social conditions. The data consist in: 1) self-report of symptoms, impairment, and duration of depression and anxiety disorders through structured questionnaire interviews; 2) reports by general physicians about the full range of psychiatric disorders; 3) a case register of a local mental health center; and 4) death certificates. A diagnostic computer program was written for analyzing information given by subjects. Using this methodology, it was found that during the period from 1952 through 1970 the prevalence of depression and anxiety remained at a stable rate of 12 cases per 100 persons and the incidence of these disorders was, on the average, nine cases per 1000 persons per year. Depression has consistently been distinguished from anxiety, including the fact that depression was found to have significantly worse outcome in terms of both mortality and morbidity. Life table methods, log-linear analysis, and survival regressions are used for calculating rates and testing the significance of associations with risk factors. The application includes research directed toward comparing findings from this investigation with those from other places study, both urban and rural. The degree of concordance between the interview methods of this study and those of more recent studies will be assessed by using the Diagnostic Interview Schedule along with the Stirling Study Schedule in the follow-up interviews to be carried out in 1990.